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Selkirks, perfect examples of the forms which gravity imparts 
to moist snow were met with. 
Fic. 1.—A Snow-mushroom nine feet in diameter. 
At Glacier House a tree stump 2 feet in diameter had a cap 
of snow 9 feet across, the eaves projecting 3 feet 6 inches all 
round the pedestal. A broken tree with 
diameter of 4 feet had a snow-cap 12 feet 
across, the eaves projecting 4 feet beyond 
the pedestal (Fig.1). Some of these snow- 
mushrooms must have weighed a ton. 
That the ‘‘ snow-mushroom ” is, on 
the whole, so remarkably preserved from 
ruin by overloading may be attributed 
to bending of the strata under the action 
of gravity, their inclination to the horizon 
increasing with the distance from the 
pedestal. 
Waves of drifting snow are only 
formed in dry snow at a low tempera- 
ture. They are not so steep as the cor- 
responding sand-waves. 
Even when the surface is all covered 
with fresh snow, an extensive horizontal 
plain appears to be the best field for the 
growth of snow-waves, for the liability 
to local sarcharge increases with the 
extent of the field of drifting. The 
more unlevel is the country, and the 
more numerous the places of shelter, 
the shorter is the time during which the 
wind can drift the snow in waves, and 
the smaller is the extension of the 
individual groups. of waves. 
Snow-fences are commonly erected in 
Canada to check the rate of snow- 
drifting. After the first snowfall, a 
snow bank or drift is produced, having 
a moderately gentle slope to windward and a cliff or 
nice on the lee side. The form resembles that of a sand- 
dune or any other wave of a drifted powder, which at first 
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| SEPTEMBER 4, 1902 
suggests that the form proper to a drift caused by the fence 
is similar to that of freely drifting snow. This, however, is not 
the case, for the structure is as yet incomplete, owing to in- 
sufficient supply of the material. Succeeding snowfalls build 
out the drift with a diminishing cliff, until we have at last, 
perhaps not until nearly the end of winter, the completed form 
in which there is no lee cliff, but a long, gently tapering slope 
on the Jee side, the weather face retaining its original form 
and re/atively steep slope. 
When we have to do with large bluffs or cliffs, the whole of 
the winter’s snow is not sufficient to fill in the area of eddies on 
_ the sheltered side so as to reduce the surface to “‘ easy lines.” 
| Thus the largest drifts are never of completed form, but have 
‘always a steep face to leeward, Completed drifts, having no 
| shadow-throwing cliffs, are also much less conspicuous rela- 
tively to their size. Thus circumstances combine to prevent 
the casual observer from discovering what is the profile really 
proper to a snow-drift. 
From an examination of the snow-drifts in Canada, the con- 
clusion was reached that a curve of the character shown in Fig. 
Fic. 
2.—The fundamental Curve of Snow-drifts. 
| 2, with the blunt end towards the wind, was the fundamental 
element of their form. 
This, which may be termed the zchthyotd curve, is the profile 
of completed drifts in the neighbourhood of obstructions on the 
prairie. 
Inverted, it is the profile of the holes round trees, as observed 
in the woods near Montreal. 
Viewed in plan, it is the curve cut out in the snow round the 
end of a wall. 
Viewed in plan together with its image, it is a boundary curve 
enclosing the horseshoe-shaped banks round houses near Winni- 
peg, and equally the hollows round trees or stones. 
This doubled curve has the generalised form of a fish,? or if it 
| be spun round so as to give the outline of a solid body, we have 
| the modern Whitehead torpedo with the blunter head now 
| preferred to the older sharp-nosed form. 
The analogy to the fish-form is still more striking if fishes 
are looked at from above instead of viewing them in profile. 
Fic. 3-—Stratification of Snow revealed by Wind Erosion. 
The completed snow-drift in the neighbourhood of an obstruc- 
1 The profile of the 
snow-crift resembles the profile of a sole cr other flat 
fish. 
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